Auto-injectors are used for clinical parenteral administration of a fixed dose of a beneficial agent to a subject. They are particularly advantageous, and hence more commonly practiced, in emergency applications in which proper administration, potentially by an untrained or minimally trained user, under extreme duress, in less than optimal conditions, is needed to be perform in a timely manner. Auto-injectors are more proper for these applications than regular syringes as they require fewer and simpler to implement operative steps. It is hence an important aspect of auto-injector design to minimize the number and complexity of the operation steps of an auto-injector. Many auto-injector technologies require two hand preparation of the device for injection, such as arming of the device, release of a safety catch, and removal of an aseptic barrier that ensure the sterility of the device until the time of use. According to one usability aspect of auto-injectors, the need to perform two hand operations introduces a level of complexity and confusion to the user, as eventually the device has to be properly repositioned, in the proper orientation, in the hand that is used for administration.
One example of an commonly used auto-injector is the EpiPen® manufactured by Meridain Medical Technologies (Columbia, Md.). The EpiPen® applies a spring force to automatically deliver a dose of epinephrine from a glass syringe. The EpiPen® requires two hand operation to remove a cap and arm the device, at the end of which the device needs to be reoriented and properly grasped by the hand that delivers the injection. Several publications describe user error in handling the EpiPen® where the user applies the wrong side of the EpiPen® auto-injector to the subject, and wasting the medication dose toward the opposite side (away from the target injection site).
U.S. Pat. No. 8,425,462 teaches an auto-injector propelled by a CO2 cartridge. The auto-injector has an actuation guard that is removable to allow activation of the device. Two hand operation is required to remove the actuation guard and prepare the device for injection. As a result, it is likely that reorientation of the device and change in hand grasp would be performed during preparation for injection.
U.S. Pat. No. 6,979,316 teaches an auto-injector operated by a spring. A molded safety cover is fitted onto the forward end of the housing and maintains the sterility of the internal components and also prevents inadvertent actuation of the device. The safety cover must be removed from the device before it can be used.
In similar fashion, other auto-injector technologies, in commercial embodiments and in published documentation, require two hand operation to prepare for injection and bare the risk of mishandling for administration.